You can use the image functions in PHP to get the size of JPEG,
GIF, PNG, SWF, TIFF and JPEG2000 images.

By using the GD library, you will also be able to create and
manipulate images. Support for TrueType and PostScript fonts 
is also included.

The format of images you are able to manipulate depend on the version
of GD you install, and any other libraries GD might need to access
those image formats. Versions of GD older than gd-1.6 support gif
format images, and do not support png, where versions greater than
gd-1.6 support png, not gif.
